a) Field of the Invention
This invention relates generally to photographic cameras, and more particularly, to focusing systems used in photographic cameras.
b) Description of Related Art
The art of creating special effects in the field of photography has been very active in the past and continues to grow with the increasing interest in photography and the desire for more interesting visual illusions. Devices have been developed, for example, to alter an image prior to or during its exposure on film. Typically, these devices are attached at the end of the lens of a camera, and directly interfere with the light prior to it reaching the film. The alterations or effects applied to the incoming light vary from common color-filtering changes to superimposing "sub-images" onto the same frame of film that is recording the "real" image. For example, placing an opaque, pre-shaped matte in front of a portion of the incoming light will block a correspondingly shaped portion of the film. This results in an unexposed area of film which may be later "filled-in" with another image to create one desired illusion or effect. Similar diffusion mattes are used in "still photography" to produce progressively under-exposed boarders to a frame of film being exposed, creating a vignette boarder.
Conventional devices have also been used to superimpose an image of characters such as a date or other alpha-numeric information onto a portion of an image on a frame of film. Typically, these devices, such as the device disclosed in U.S. Pat. No. 1,504,959 issued to Leschbrandt, include a translucent plate (or ribbon) having, for example, opaque characters positioned at the film plane in a camera. The plate of characters is aligned adjacent to and in front of the surface of the film. Light from an external source or light generated from within the camera is used to superimpose selected characters of the plate onto a portion of the film.
U.S. Pat. No. 3,916,423, issued to Ueda et al. discloses a device for transposing information (characters, lines or designs) onto the surface of film during exposure of the film to an image. A transparent plate having an opaque mask is attached to a film cartridge in front of and adjacent to a frame of film. During exposure, a portion of the light from the image is blocked by the opaque mask located on the transparent plate prior to the light reaching and exposing the film. The result is under-exposed regions of the film (negative) corresponding to the particular shape of the opaque mask. When the negative is used to expose a positive print, the shape of the particular opaque mask will be positively transposed in the form of dark overexposed regions in the final print.
One limitation with these prior art special effects devices is that they all rely on blocking a portion of the incoming light prior to the light reaching the film. Although many effects may be created using the prior art methods employing opaque masks, many other effects require more subtle, diffusion methods.
Oftentimes, when a photograph is taken of a particular subject within a particular scene, the lighting conditions and lighting distribution within the scene and the reflective characteristics of the subject will cause areas on the film negative to become either overexposed or underexposed relative to the "normal" exposure range of the film. A conventional camera usually includes at least one integral light meter which is used to measure the average intensity of light entering the camera prior to exposing the film. The light meter generates an electrical signal that is interpreted by a computer and is used to control either the size of the aperture of the lens, the speed of the shutter, or both, so that the average intensity of light is compensated throughout the entire picture, as recorded by the film. With some more advanced cameras, such as the N-90, N90s, and F5 cameras manufactured by Nikon.RTM. of Japan, several separate light meters are used, each measuring the intensity of light within a particular zone or region of the frame (an upper region is used to measure the intensity of light from the sky of the scene, for example. Although the use of several light meters to measure the different light intensities at different regions of a framed scene provides a more accurate average light intensity reading, the camera cannot control the amount of light from a particular region of the framed scene reaching the corresponding region of the film without effecting the amount of light reaching the other regions of the film. In other words, the overall density of the negative can be corrected by adjusting either the aperture of the lens or the operating speed of the shutter, however, this exposure correction has a uniform effect over the entire recording area of the film (i.e., the frame). If the aperture is decreased to lessen the amount of light reaching the film to compensate for the "bright" spots of the subject or scene, for example, the otherwise "neutral" or normal areas of the subject or scene will now become too dark. If the speed of the shutter is prolonged to "burn in" the darker regions of the image, the normal areas will become unacceptably overexposed and appear "washed out".
Unfortunately, since a conventional camera merely measures the average of the total received light entering the camera of a particular image, many pictures end up with a portion of the recorded image either overexposed (to dark) or underexposed (washed out).
In an attempt to prevent this relatively common exposure malady from ruining an otherwise good picture, serious photographers have made it common practice to take several pictures of the same image (i.e., bracket the image) and then vary the exposure of the image between each shot, (typically around 1/3 EV) so that each image offers a slightly different exposure from which the photographer may later select the recorded image that averages the received light most accurately. The above-identified N-90 manufactured by Nikon.RTM. offers a bracketing feature with its M-26 data-back accessory which allows the camera to automatically take a selected number of pictures and vary the exposure a preset degree between shots.
There are several problems with the bracketing technique of photography. Not only is a lot of film exposed for few different images, only relatively expensive cameras offer exposure control, let alone automatic bracketing of the exposure. Also, although exposure bracketing provides several pictures to select from, since the camera's exposure meter must account for the total received light and may not locally correct the exposure of a portion of the image frame, all of the bracketed pictures will show varying degrees of over and under-exposure. In other words, if there is an overexposed region of an image, bracketing will not correct the exposure of that particular region, merely hide it by changing the total exposure throughout the image, as recorded by film.
Other attempts have been made to control the exposure of a particular region of a frame of film, without effecting the exposure of the other regions of the frame of film. Special segmented, or zone filters include regions of varying opacity which may be aligned within a particular scene to compensate for highlighted regions, such as a cloudy sky. These filters rarely align with the image detail and are only useful when the specific regions defined by the filter align with the regions of the scene.
Once a negative is developed, any underexposed or overexposed regions may be compensated during the production of a photographic print using well known techniques known as "dodging" or "burning" in which a density mask (made from opaque and semi-transparent sheet material) is held in the exposure path (over the photographic paper) when a print is being made from a negative. The mask is used to selectively protect overexposed areas of the negative from a portion of the light projected to the photographic paper during image enlargement (or print processing). However, these techniques are used in expensive custom print processing, not in cheaper automated print processing. These techniques are difficult to uniformly perform on a repeated basis because of the inherent inaccuracies in placing the density mask in the proper location each time a print is made and also require a great amount of time to adjust the mask from print to print. Furthermore, the results of these exposure compensating techniques are not known until after the print is exposed and developed. If the results are unsatisfactory, another attempt must be made in a trial-and-error method until a satisfactory print is produced.
Grain Effects
Although the art of photography is always open to creative input, as a general rule, good image quality of photographs tends to include some consistent characteristics. Among these involve sharpness, tonal depth, and graininess, which are each somewhat related. Using conventional film (and assuming an image has been recorded in focus on the film), sharpness tends to be directly related to the film's ISO speed wherein the lower the film's ISO speed, such as 25 ISO, the finer the grain and the sharper the image (i.e., the image will be recorded by the film at a higher resolution because the grain of the emulsion is finer). High speed films, such as 1600 ISO have a tendency to record an image with high grain characteristics, resulting in a somewhat blurred image revealing "soft" detail.
The term "grain" in photography is used to describe the granular texture that appears, to some degree, in all processed photographic materials. In black and white photography, the grains are minute particles of black metallic silver which constitute the dark areas of a photograph. In color photography, although the metallic silver is chemically removed during processing, extremely fine blotches of dye remain on the film and retain the appearance of "grain".
The emulsion grain of film may be considered analogous to the pixel resolution of a television set. The finer the resolution of the television screen, the finer the "grain", and the sharper an image will appear on the screen. Similarly, should the resolution (or number of pixels per inch) be reduced (and thereby increased in size), the more noticeable each pixel (or grain) will be, and therefore, the less sharp the image will appear. Since each grain, (or pixel in a TV set) translates a single representative tonal shade of the gray scale, the finer the grain, the higher the "sampling" rate over a given area of an image and the more accurate the tonal depth or tonal transition (transition from white to black regions of the image) will be recorded on the film.
Since emulsion grain tends to "dull" an image by lowering the recorded resolution of the film, this film characteristic is generally considered undesirable and much research and development has been directed to eliminating (or at least minimizing) the effects of grain from any processed photograph, either at the transparency or negative stage, or in the final print. Graininess is also generally undesirable by photographers because by achieving high grain in a negative, the tonal depth of the image is adversely effected, as described above. Coarse (or high) grain within a negative or picture tends to digitize an image so that each "grain" (or pixel) or in some cases, each grain cluster (a group of grains within the emulsion of the film) translates a real image having a gradation of tones including several shades of gray (at a particular region of the image) into a single shade of gray on the film. This digitizing of the tonal information of the image tends to create a dull, choppy, high-contrast, recorded image having little tonal depth or realism.
As discussed above, graininess of film is generally a factor of film speed, however, a low-speed film (100 ISO) which should normally result in a fine grain representation of an image, may be "pushed" during processing of the film so that the film is developed as if it were a higher speed film, such as 400 ISO film. In such instance, the emulsion grain may appear coarser than normal. Similarly, higher speed film may be "pulled" during processing so that it is processed as if it were a lower-speed film. In doing so, grain size and grain effect may be altered.
Although emulsion grain is typically associated with poor image quality, as discussed above, it can be used beneficially to create a certain mystique and/or softness of a subject that is otherwise difficult to obtain, using, for example, conventional soft-filter techniques known in the art. It is known, for example, to introduce a grain effect during the enlargement process wherein an image of a normal negative is enlarged (or at least transposed) onto photographic paper. As is known by those skilled in the art, a negative is positioned within and held by a negative carrier. The negative carrier is then positioned within an enlarger so that light may pass through the held negative and its exposed image projected onto a sheet of photographic paper. To create a grain-like effect during the enlargement process, a potato starch may be applied to a glass plate located adjacent to the negative within the negative carrier. The potato starch layer creates a "stochastic screen" which comprises millions of"grain-like" structures of the transparent potato starch. This procedure is described in U.S. Pat. No. 822,532 to Auguste and Louis Lumiere, issued Jun. 5, 1906, and the process is currently used by LTI Labs of New York, N.Y. Although this process creates a grain-like structure on photographic paper simultaneously with the exposure of the image of the negative, the resulting grain is not effectively controllable and will vary in size and texture depending on the size of enlargement being made, the larger the print, the larger the grain. Also, this process of using potato starch to introduce a grain-like characteristic to a photographic print is considered custom photographic work and is inherently expensive to implement, by only select professional photographic labs.
Applicant has recognized the value of selectively introducing grain effects in a controlled manner to an image without effecting other characteristics of the photograph, such as tonal depth and sharpness.
Focus Control
During the past century, since the invention of the still-type film camera, photographic technology has introduces many different types of cameras, usually identified by the format of film used. Today, three main types of still-type film cameras are commercially available, 35 mm cameras (including point and shoot type camera, disposable cameras, single lens reflex cameras, and rangefinder type cameras), medium format cameras (including twin-lens), and large format cameras (including field-type and view type). These cameras use one of at least six basic systems of focusing: (1) fixed-focus, (2) "zone-focus", (3) rangefinder, (4) twin-lens reflex ground glass, (5) single-lens reflex, and (6) automatic focus.
In a fixed-focus camera, such as a conventional disposable type camera, there is no means to control the focus of the lens. The focus of the lens is pre-set in the factory to provide acceptable focus at a predetermined distance (usually around 10 feet). This type of camera is essentially a pin-hole camera with a lens.
Camera operators using "zone-focus" cameras must estimate (or actuallymeasure) the distance between the camera and the subject and use this information to control the focus of the lens so that the subject is reproduced in focus at the film plane of the camera.
A rangefinder focusing system uses an optical-mechanical device that produces two images in a viewfinder of the camera. The focusing device effectively functions as a distance measurer (or rangefinder) to help the operator determine the distance between the subject and the camera. In operation, as the operator adjusts the focus control of the lens, the two images within the viewfinder move with respect to each other. A subject is in focus when both images overlap and appear as one image within the viewfinder.
A twin-reflex camera uses two identical lenses that include synchronized focus controls so that both lenses move simultaneously. One lens focuses an image onto a focusing screen for the operator while the other lens focuses essentially the same image onto the film plane. When the operator adjusts the first lens so that the image is in focus on the focusing screen, the second lens will be properly adjusted so that the image will also be in focus at the film plane.
The single-lens reflex focusing system (or SLR) is one of the most popular focusing systems used in today's cameras. This type of focusing system allows the operator to view the actual image that will be recorded by the film. A pivotal mirror rests in the path of incoming image light and is used to direct the image light from the lens to a focusing screen, which may be viewed by the operator through an eyepiece. When the shutter release button of the SLR camera is depressed, the pivotal mirror immediately pivots away from the path of incoming image light and allows the image light to continue to the film gate and film. This type of focusing system allows the operator to "sample" or test the focus adjustments of the particular lens before any film is exposed.
Finally, cameras that automatically focus include a battery-powered motor drive unit that directly controls the focus of the particular lens assembly, and at least one type of electronic distance sensor, such as sonar, infrared, or phase-contrast. The sonar and infrared sensors essentially determine the distance between the subject and the camera and then cause the motor to control the focus of the lens accordingly. The phase-contrast system measures the contrast of adjacent lines of the incoming image light and similarly, uses this information to control the focus of the lens.
Motion-film cameras or movie cameras typically use a zone-focusing system wherein the camera operator (or an assistant) will actively control the focus of a lens during a particular shoot. If the subject advances towards (or recedes away from) the camera, the camera operator may have to "rack focus" the lens during a shoot to maintain the moving subject within the depth of field of the lens and in focus on the film. Regardless of how the focus of a particular lens is adjusted, most of the motion-film cameras used today allow the cameraman to view the image through the lens (i.e., in an SLR manner).
Most of the above-described focusing systems are limited in that they are designed to focus an image evenly across the field of view as centered about a lens pupil (or a center axis). Furthermore, the focus of a lens is dependent on the depth of field of the particular lens. In turn, the depth of field is affected by the lens aperture, the focal length of the lens, and the distance between the camera and the subject. For example, a telephoto lens (having a large focal length) will yield a short depth of field (or depth of focus), resulting in only a portion of an object in the field of view being in sharp focus. In contrast, the depth of field of a wide angle lens (having a relatively short focal length) is close to infinite resulting in all objects in the field of view (foreground and background) being in sharp focus. To this end, should a director wish to create a mood or mystique within a particular shot, by softening or de-focusing part of an image, for example, only foreground actors while maintaining a mid-ground subject in focus, the director would be restricted to lenses having mid to long focal lengths (e.g., telephoto) to obtain the desired selective de-focusing affect. Unfortunately, lenses with long focal lengths require a minimum focusing distance, typically between 10 and 20 feet. To achieve the desired selective de-focusing affect, the director must now position the camera at least 10 feet from the subject. This minimum focusing distance requirement may not easily be met depending on the particular scene being shot. For example, the scene may be located within an elevator or a submarine, or any other close-quartered environment wherein the minimum focusing distance requirement cannot be achieved without building a "specialized movie set", or using soft-focusing techniques.
A common effects technique used in both still and motion photography to selectively de-focus or soften selective regions of a particular scene includes the use of a translucent medium, such as tissue paper, petroleum jelly or a frosted glass plate. The technique includes applying the translucent medium directly to (or positioning it in front of) the camera lens. The translucent medium effectively diffuses a select portion or region of image light entering the camera so that the resulting recorded image is softened and selected detail is diluted. Although this de-focusing technique is somewhat effective at creating soft, de-focused regions of an image frame, the technique requires substantial setup time prior to shooting, and substantial clean-up time after the shoot. Also, the technique is difficult to control accurately in selecting exact image regions to dc-focus, and is further difficult to reproduce when a re-shoot is necessary.
Another technique available to photographers to de-focus or otherwise soften selected regions of an image frame includes a "shift and tilt" mechanism which pivotally connects a lens to a camera body. The shift and tilt mechanism allows a lens to both pivot and laterally shift with respect to a central optical camera axis, thus enabling a controlled distortion of selected regions of an image frame (to "shift" the lens means to slide it parallel to the viewfinder image, while keeping the lens' optical axis at right angles to the film plane). By tilting the lens up or down (or left or right), photographers can change the angle between the optical axis and the film plane. This lets the photographer modify the plane of focus in the resulting photographs to get a variety of effects. One such effect is the ability for the photographer to focus just a specific part of the subject. A shift and tilt mechanism is used in most large format cameras and is available (as an attachment) for use with motion picture cameras. The mechanism is difficult to use and is subject to unwanted distortion, unless any of a limited number of dedicated lenses are used, which severely limits the director's creativity and control. Also, the regional focus-control offered by the shift and tilt mechanism is limited to single peripheral regions of the image frame, not multiple internally located regions, such as a central region.
It is accordingly an object of the invention to provide a focusing system for use with a camera which overcomes the limitations of the prior art.
It is another object of the invention to provide a focusing system for use with a camera which allows select regions of an image frame to be purposely de-focused in a controlled and efficient manner.
It is accordingly an object of the invention to provide optically-generated grain effects to film without adversely effecting other characteristics of the film.
It is another object of the invention to provide a special effects device for use in photography which overcomes the limitations of the prior art.
It is another object of the invention to provide such a device which enables a photographer to transform photographic images into images having characteristics inherent in paintings of such images.
It is another object of the invention to provide such a device which enables a photographer to superimpose a translucent mask including random crackling onto an image, resulting in a final print which includes the craquelure characteristics of aged oil paintings.
It is another object of the invention to provide such a device which enables a photographer to superimpose a translucent mask onto an image to transpose the image to one having characteristics inherent in a water color painting.
It is another object of the invention to provide such a device which enables a photographer to superimpose a translucent mask onto an image to transpose the image to one having characteristics inherent in an oil pallet-knife type painting.
It is another object of the invention to provide a method and apparatus for producing a photographic negative wherein areas of overexposure and underexposure may be corrected prior to the film being exposed.
It is another object of the invention to provide a regional exposure correction to selected regions of an image to be recorded on film, wherein the regions may follow the specific contours of a scene, object or subject located within the image.
It is another object of the invention to provide a preview image of an exposure-corrected image prior to the image being recorded on film.
It is yet another object of the invention to provide various degrees of regional exposure correction to an image.
It is yet another object of the invention to provide a method and apparatus for selectively modifying an image using a single modifier located adjacent to the film.
It is yet another object of the invention to provide movement of a selected modifier during exposure so that a multitude of effects can be generated from a single modifier.